Micro-blogging has become an effective means for collaborative discussion by allowing participants to share information at any given moment on a topic. In the Yammer® micro-blogging service, each participant is included in a social network that is associated with the domain portion of their email address. For example, if Joe (joe@foo.com) and Bob (bob@foo.com) register with Yammer®, then both are automatically included in the foo.com social network. Further, if Mike (mike@loo.com) and Greg (greg@loo.com) register with Yammer®, then both are automatically included in the loo.com social network.
Increasing the number of individuals who are members of social networks in the micro-blogging service of Yammer® is desirable. In fact, social networks in general strive to increase the number of users since a large number of users enhances the comprehensiveness and relevance of the information shared by the users in the social networks. There is also a certain critical mass that needs to be achieved to make any social network useful. In particular, the frequency at which a user is likely to participate in a social network corresponds significantly to the amount of information that is presently available in the social network and the number of users that are participating in the social network.
Presently, several techniques are used to promote users of a social network to invite their colleagues, friends, and/or family to join. In one such technique, contacts included in the address book of users of the social network are invited to join the social network. These invitations are automatically generated from a user's address book when the user registers with a social network. However, such invitations are often viewed by recipients as spam due to the increased frequency at which they are being generated. As a result, the invitations are mostly ignored and fail to provide any substantial growth to the social network.